Unique Running Pattern and Mucosal Morphology Found in the Colon of Cotton Rats

Abstract

Cotton rats are one of the experimental rodents used for testing different infectious and non-infectious diseases, including gastrointestinal tract pathology. However, their intestinal morphological characteristics are still poorly understood. Here, we clarified the anatomical and histological characteristics of the cecum and ascending colon (AC) of young (1-3-month old), adult (4-6-month old), and old (10-12-month old) cotton rats. The large intestine (LI) in cotton rats is composed of the cecum, AC, transverse and descending colons, and rectum, and is similar to that of other mammals. The AC begins with a double or triple spiral loop-like flexure (SLLF) and ends with a coupled horseshoe-like flexure (HSLF). A single longitudinal mucosal fold (SLMF) was found at the beginning of the AC along the mesentery line and developed with age. Furthermore, the SLMF contained several lymphatic nodules (LNs), indicating their role in digestive and immunological functions. Small and large protuberant LNs were found in the cecum and SLLF, respectively, whereas thin and flat LNs were observed in the HSLF and transverse colon, respectively. Regarding sex-related differences, adult females had a significantly longer AC with a higher number of SLLFs compared to males. The SLMF length and LN number were also longer and higher, respectively, in adult females compared to adult males. These are crucial findings, indicating the presence of sex-related differences in the morphology of the LI in cotton rats, and ours is the first study to discover a sex difference in the mammalian LI lining. Our study clarified the unique morphology of the LI in cotton rats, which could serve as the principal model for elucidating species-specific digestive tract functions and gastrointestinal disorders.

Morphological Characteristics of Genital Organ-Associated Lymphoid Tissue in the Vaginal Vestibule of Goats and Pigs

“…Furthermore, lymphocytes and dendritic cells infiltrate the epithelium overlying the MALT [ 1 ]. In aquatic and terrestrial animals, MALTs are classified according to their anatomical location as follows: lymphoid tissues of Waldeyer’s ring—lingual, palatine, paraepiglottic, pharyngeal, and tubal tonsils and the tonsil of the soft palate [ 2 ]; conjunctiva-associated lymphoid tissue, nose or nasopharynx-associated lymphoid tissue; bronchus-associated lymphoid tissue, gut-associated lymphoid tissue (GALT), larynx- and trachea- associated lymphoid tissue, (salivary) duct-associated lymphoid tissue, lacrimal duct-associated lymphoid tissue, and genital organ-associated lymphoid tissue (GOALT) [ 2 , 3 , 4 , 5 , 6 ].…”

Cotton rats (Sigmodon hispidus) with a high prevalence of hydrocephalus without clinical symptoms

“…We here report that cotton rats have noticeable systemic pathological phenotypes, such as chronic kidney disease with anemia, metabolic disorders, and false caudal autotomy. [10][11][12][13][14] Additionally, these species possess unique phenotypes in endocrine, reproductive, and digestive organs, [15][16][17][18] suggesting that cotton rats might be useful experimental animal models. However, the central nervous system (CNS) of cotton rats has not yet been investigated.…”